Polyphenylene ether resins are noted as engineering resins having excellent mechanical and thermal properties.
However, the polyphenylene ether resins when used alone are seriously inferior in solvent resistance. In order to overcome this drawback, it has been proposed to blend the polyphenylene ether resins with polyamide-based resins as disclosed in Japanese patent publication No. 41663/84 (corresponding to U.S. Pat. No. 4,338,421), or with polyester-based resins as disclosed in Japanese patent publication Nos. 21662/76, 21663/76 and 21664/76. Although these polymer blends exhibit improved solvent resistance, they do not always satisfy conditions required for practical use in industry due to insufficient mechanical strength, especially impact strength. Also, the polyphenylene ether resins when used alone are inferior in moldability and impact strength other than in solvent resistance. In order to overcome these drawbacks, it has been proposed to blend the polyphenylene ether resins with high impact polystyrene. This polymer blend is now made use of, but its application is limited because of so poor resistance to solvent.
For the purpose of improving impact strength of the resin composition comprising polyphenylene ether resins and polyamide-based resins, incorporation of a liquid polybutadiene polymer [Japanese patent laid-open application No. 10642/82 and Japanese patent publication No. 11966/85 (each corresponding to U.S. Pat. No. 4,315,086)] or of a rubbery material and a compound containing a carboxyl group, an imido group, an epoxy group, etc. (Japanese patent laid-open application No. 49753/81) thereto has been proposed. These resin compositions, though showing an improvement in solvent resistance, do not always attain the levels required in the industrial field in terms of impact strength and tensile elongation indicative of toughness in the vicinity of room temperature and in terms of low temperature impact strength.
The inventors have previously found that a resin composition comprising a polyphenylene ether resin, a polyamide resin, and a partially hydrogenated aromatic vinyl compound-conjugated diene block copolymer to which maleic anhydride, etc., is grafted shows high impact strength as well as a good balance of other mechanical properties and is useful as a molding material for industrial parts, such as exterior automotive trims, etc., as disclosed in Japanese patent application No. 220737/85.
However, the proposed resin composition does not always meet the relatively severe requirements in the industrial field in terms of low temperature impact strength, tensile elongation, and the like. Besides, the resin composition leaves room for improvement on cost incurred.